target/avr: CPU class: Add GDB support

This includes GDB hooks for reading from wnd wrtiting to AVR
registers, and xml register definition file as well.

[AM: Split a larger AVR introduction patch into logical units]
Suggested-by: Aleksandar Markovic <aleksandar.m.mail@gmail.com>
Co-developed-by: Michael Rolnik <mrolnik@gmail.com>
Co-developed-by: Sarah Harris <S.E.Harris@kent.ac.uk>
Signed-off-by: Michael Rolnik <mrolnik@gmail.com>
Signed-off-by: Sarah Harris <S.E.Harris@kent.ac.uk>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Aleksandar Markovic <aleksandar.m.mail@gmail.com>
Acked-by: Igor Mammedov <imammedo@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
[thuth: Fixed avr_cpu_gdb_read_register() parameter]
Signed-off-by: Thomas Huth <huth@tuxfamily.org>
Message-Id: <20200705140315.260514-7-huth@tuxfamily.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

5 files changed, 140 insertions, 0 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index dda872ef2a..7833db3abe 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -171,6 +171,7 @@ AVR TCG CPUs
 M: Michael Rolnik <mrolnik@gmail.com>
 R: Sarah Harris <S.E.Harris@kent.ac.uk>
 S: Maintained
+F: gdb-xml/avr-cpu.xml
 F: target/avr/
 
 CRIS TCG CPUs
diff --git a/gdb-xml/avr-cpu.xml b/gdb-xml/avr-cpu.xml
new file mode 100644
index 0000000000..c4747f5b40
--- /dev/null
+++ b/gdb-xml/avr-cpu.xml
@@ -0,0 +1,49 @@
+<?xml version="1.0"?>
+<!-- Copyright (C) 2018-2019 Free Software Foundation, Inc.
+
+     Copying and distribution of this file, with or without modification,
+     are permitted in any medium without royalty provided the copyright
+     notice and this notice are preserved.  -->
+
+<!-- Register numbers are hard-coded in order to maintain backward
+     compatibility with older versions of tools that didn't use xml
+     register descriptions.  -->
+
+<!DOCTYPE feature SYSTEM "gdb-target.dtd">
+<feature name="org.gnu.gdb.riscv.cpu">
+  <reg name="r0" bitsize="8" type="int" regnum="0"/>
+  <reg name="r1" bitsize="8" type="int"/>
+  <reg name="r2" bitsize="8" type="int"/>
+  <reg name="r3" bitsize="8" type="int"/>
+  <reg name="r4" bitsize="8" type="int"/>
+  <reg name="r5" bitsize="8" type="int"/>
+  <reg name="r6" bitsize="8" type="int"/>
+  <reg name="r7" bitsize="8" type="int"/>
+  <reg name="r8" bitsize="8" type="int"/>
+  <reg name="r9" bitsize="8" type="int"/>
+  <reg name="r10" bitsize="8" type="int"/>
+  <reg name="r11" bitsize="8" type="int"/>
+  <reg name="r12" bitsize="8" type="int"/>
+  <reg name="r13" bitsize="8" type="int"/>
+  <reg name="r14" bitsize="8" type="int"/>
+  <reg name="r15" bitsize="8" type="int"/>
+  <reg name="r16" bitsize="8" type="int"/>
+  <reg name="r17" bitsize="8" type="int"/>
+  <reg name="r18" bitsize="8" type="int"/>
+  <reg name="r19" bitsize="8" type="int"/>
+  <reg name="r20" bitsize="8" type="int"/>
+  <reg name="r21" bitsize="8" type="int"/>
+  <reg name="r22" bitsize="8" type="int"/>
+  <reg name="r23" bitsize="8" type="int"/>
+  <reg name="r24" bitsize="8" type="int"/>
+  <reg name="r25" bitsize="8" type="int"/>
+  <reg name="r26" bitsize="8" type="int"/>
+  <reg name="r27" bitsize="8" type="int"/>
+  <reg name="r28" bitsize="8" type="int"/>
+  <reg name="r29" bitsize="8" type="int"/>
+  <reg name="r30" bitsize="8" type="int"/>
+  <reg name="r31" bitsize="8" type="int"/>
+  <reg name="sreg" bitsize="8" type="int"/>
+  <reg name="sp" bitsize="8" type="int"/>
+  <reg name="pc" bitsize="8" type="int"/>
+</feature>
diff --git a/target/avr/cpu.c b/target/avr/cpu.c
index be06875225..05dd5551c7 100644
--- a/target/avr/cpu.c
+++ b/target/avr/cpu.c
@@ -210,4 +210,8 @@ static void avr_cpu_class_init(ObjectClass *oc, void *data)
     cc->disas_set_info = avr_cpu_disas_set_info;
     cc->tcg_initialize = avr_cpu_tcg_init;
     cc->synchronize_from_tb = avr_cpu_synchronize_from_tb;
+    cc->gdb_read_register = avr_cpu_gdb_read_register;
+    cc->gdb_write_register = avr_cpu_gdb_write_register;
+    cc->gdb_num_core_regs = 35;
+    cc->gdb_core_xml_file = "avr-cpu.xml";
 }
diff --git a/target/avr/cpu.h b/target/avr/cpu.h
index 99875e50b1..8d99122804 100644
--- a/target/avr/cpu.h
+++ b/target/avr/cpu.h
@@ -123,6 +123,8 @@ extern const struct VMStateDescription vms_avr_cpu;
 void avr_cpu_do_interrupt(CPUState *cpu);
 bool avr_cpu_exec_interrupt(CPUState *cpu, int int_req);
 hwaddr avr_cpu_get_phys_page_debug(CPUState *cpu, vaddr addr);
+int avr_cpu_gdb_read_register(CPUState *cpu, GByteArray *buf, int reg);
+int avr_cpu_gdb_write_register(CPUState *cpu, uint8_t *buf, int reg);
 
 #define cpu_list avr_cpu_list
 #define cpu_signal_handler cpu_avr_signal_handler
diff --git a/target/avr/gdbstub.c b/target/avr/gdbstub.c
new file mode 100644
index 0000000000..c28ed67efe
--- /dev/null
+++ b/target/avr/gdbstub.c
@@ -0,0 +1,84 @@
+/*
+ * QEMU AVR gdbstub
+ *
+ * Copyright (c) 2016-2020 Michael Rolnik
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see
+ * <http://www.gnu.org/licenses/lgpl-2.1.html>
+ */
+
+#include "qemu/osdep.h"
+#include "exec/gdbstub.h"
+
+int avr_cpu_gdb_read_register(CPUState *cs, GByteArray *mem_buf, int n)
+{
+    AVRCPU *cpu = AVR_CPU(cs);
+    CPUAVRState *env = &cpu->env;
+
+    /*  R */
+    if (n < 32) {
+        return gdb_get_reg8(mem_buf, env->r[n]);
+    }
+
+    /*  SREG */
+    if (n == 32) {
+        uint8_t sreg = cpu_get_sreg(env);
+
+        return gdb_get_reg8(mem_buf, sreg);
+    }
+
+    /*  SP */
+    if (n == 33) {
+        return gdb_get_reg16(mem_buf, env->sp & 0x0000ffff);
+    }
+
+    /*  PC */
+    if (n == 34) {
+        return gdb_get_reg32(mem_buf, env->pc_w * 2);
+    }
+
+    return 0;
+}
+
+int avr_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
+{
+    AVRCPU *cpu = AVR_CPU(cs);
+    CPUAVRState *env = &cpu->env;
+
+    /*  R */
+    if (n < 32) {
+        env->r[n] = *mem_buf;
+        return 1;
+    }
+
+    /*  SREG */
+    if (n == 32) {
+        cpu_set_sreg(env, *mem_buf);
+        return 1;
+    }
+
+    /*  SP */
+    if (n == 33) {
+        env->sp = lduw_p(mem_buf);
+        return 2;
+    }
+
+    /*  PC */
+    if (n == 34) {
+        env->pc_w = ldl_p(mem_buf) / 2;
+        return 4;
+    }
+
+    return 0;
+}